I have played a decent amount of both, but currently I am focusing on tournaments. The reason is, I got a little bored with cash games, and I also think, tournaments tend to be softer and have less effective rake, which makes it easier to win money and build up a decent
bankroll.
The main drawback is, tournaments are much more unflexible. You need to wait for a certain tournament to start, and then you are stuck with it, until you win or bust. Which might be 10 minutes or 6 hours. With cash games you can come and go, as you like, so I totally understand, why many still prefer that format.